The present invention relates to a device and a method for setting a press-in element. The present invention especially relates to a device and a method for setting a press-in element into a workpiece consisting of plastic or fiber composite material, such as CFK, especially in vehicle construction, at a predetermined point.
In many applications, the use of plastics, especially fiber-reinforced plastics, is increasingly common. This is especially the case in vehicle construction, including automobile construction, aircraft construction, ship building and other vehicle applications, as well as also in the production of everyday objects. The production of connections to other workpieces in the case of molded parts consisting of plastic is often difficult, however. In automobile construction, it is known, for example, to realize load application points on fiber composite workpieces via bonded studs or the like. The problems in this case are the exact positioning, the surface requirement for the bonded connection, and the durability of the bond under specific environmental conditions (e.g. temperature, moisture, exposure to light, alternating stress, etc.). From boat building it is also known, for example, to realize a load application point on a fiber composite workpiece by a threaded fastening using a back-fitting metal plate which carries a connecting element. Here also, a corresponding surface requirement is to be taken into consideration, and in addition material pairing problems, such as corrosion on connecting surfaces of metals to workpieces consisting of carbon fiber-reinforced material and the like, are possible. From prosthetics, a direct screwing in of threaded bolts consisting of a fiber composite material in bone tissue (which can be understood as a natural fiber composite material) is known. In technical fields of application of fiber composite materials this is usually not possible since there can be a significant risk of damage and/or failure, depending on the load case. In general, it is also known from fiber composite technology to integrate, such as to cast, to embed or the like, connecting elements directly into a laminate workpiece or a plastic workpiece. Such fastening elements are then to be positioned already in the wet phase of the production of the workpiece and are subsequently not variable.
It is also known from metal constructions to use press-in elements such as press-in nuts, press-in threaded bolts, press-in eyelets or the like, especially in shell-like or plate-like workpieces for the realization of load application points. In this case, holes are introduced into the workpiece such as by drilling or stamping, and then the press-in element is pressed into the hole by machine or manually using a setting tool. A plastic material deformation on the workpiece and/or on the press-in element, which consequently incurs an inseparable connection at least in the region of a design load, typically takes place in this case. Such solutions are known, for example, as set rivets, rivet nuts, press-in nuts or the like. In fiber composite materials, this procedure is poor in its application since deformations of the material can lead to irreversible material damage.
The present invention starts from the consideration of setting a press-in element in a workpiece, especially consisting of plastic or fiber composite material, such as CFK (with carbon fiber-reinforced plastic) or the like, in a way that a cylindrical section of a press-in element is to be pressed into a hole of a workpiece (possibly having, though not always necessarily, an increased material thickness at the point in question), wherein the cylindrical section of the press-in element has a suitable oversize compared with the hole so that a retention force or extraction force is created essentially via the face pressure between the hole and the cylindrical section of the press-in element. A variable pressing by means of additional form fitting via, for example, locking hooks, is similarly contemplated. A challenge in this case is that the pressing-in has to take place with high positional accuracy since an already slight lateral misalignment in the order of magnitude of, for example, 1/100 mm or an angular inaccuracy in a corresponding magnitude could partially lead to the plastic or composite material at one point experiencing an excessively high face pressure. This can lead to damage so that overall a reduced pressing force, possibly even a clearance, which can significantly reduce the extraction force of the press-in element from the workpiece, is created. Up to now, no method and no mechanical realization has been known by which such a pressed connection can be produced with sufficient process reliability in order to reliably ensure the necessary positional and angular accuracies during the pressing-in.
In more general terms, no (material-perfect) fiber composite—suitable solution for implementation of a threaded connection and/or fastening of further workpieces to endless fiber-reinforced plastic workpieces has been available since the implementation of a threaded connection is often accompanied by damage to the fiber composite.
It is therefore an object of the present invention to provide a device and a method which at least partially avoids the disadvantages of the prior art, as previously described. In particular, an object of the present invention entails providing a device and a method which enable a process-reliable introduction of connecting points on fiber-reinforced workpieces or on other plastic workpieces.
The aforesaid object is achieved at least in partial aspects by way of a device according to embodiments of the invention and a method according to embodiments of the invention. In this case, features and details, which are described in conjunction with the device according to the invention, also apply in conjunction with the method according to the invention and reciprocally and interchangeably in each case so that reference is always made, or can be made, reciprocally with regard to the disclosure of the individual aspects of the invention.
Proposed according to one aspect of the present invention is a device for setting a press-in element into a workpiece, especially consisting of plastic or fiber-reinforced material such as CFK, especially in vehicle construction, at a predetermined point, wherein the device includes:                a basic body;        a fixing unit, attached to the basic body, which is designed for the fixing of the basic body;        and a processing unit, which is attached on the basic body and includes:        a drilling unit, which is designed for introducing a hole in the workpiece which is fixed by use of the fixing unit; and        a pressing-in unit, which is designed for pressing a press-in element into the hole.        
Within the meaning of the invention, a structural unit which forms a spatial reference and a constructional add-on structure for further units of the device is to be understood by a basic body. The basic body can be handled separately or can be part of a larger system. Meant by a fixing within the meaning of the invention is a fastening of the workpiece in such a way that the workpiece is immovable, at least during the processing by the device, in relation to the fixing unit—and therefore in relation to the device itself. The fixing especially comprises a detachable fastening, for example, but not exclusively, by clamping, gripping, suction, etc. The term attaching within the meaning of this aspect of the invention can be a joining, for example, but not exclusively, by screwing, welding or the like. In a broader sense, attaching can also be a fixed supporting or, providing the previously explained effects of the invention are not impaired thereby, can comprise a movable supporting or guiding. For example, the attaching of the processing unit on the basic body comprises a joining of fixed supporting of the processing unit on the basic body, especially if the fixing of the workpiece is carried out separately for each setting process. In one modification, the attaching of the processing unit can comprise a supporting on the basic body in such a way that the processing unit is movable to a certain extent with regard to the workpiece in order to be able to carry out processing procedures at a plurality of predetermined points without releasing the fixing of the workpiece. In this case, the predetermined points can be approached by moving the processing unit, wherein the movability of the processing unit at the predetermined points can be fixed by locking, braking means or fixing bodies, by a toothed wheel engagement, or by other measures.
The proposed device of this aspect of the present invention enables a substantial simplification of the setting process since drilling and pressing in are possible by use of one and the same device. Furthermore, an accurate positioning and pressing in at the predetermined point can be ensured since the workpiece is fixed on the basic body. By integrating the drilling unit and the press-in unit on a processing unit, a deviation when pressing the press-in element into the hole can be minimized and the required pressing in quality can be achieved. The processing unit, in other words, forms a mounting or guide for the drilling and press-in unit (which can also be referred to as the tools of the device) so that positional relationships of the workpiece, of the basic body and of the tools, apart from manufacturing tolerances, bearing clearances and elasticities, are determined.
In one development of the present invention of this aspect, the processing unit is designed in order to selectively bring the drilling unit or the press-in unit into a predetermined working position corresponding to the predetermined point, wherein a working axis of the drilling unit, when the drilling unit is located in the working position, and a working axis of the press-in unit, when the press-in unit is located in the working position, coincide at least for the most part. In this case, the working axis of the drilling unit can also be referred to as the drilling axis and the working axis of the press-in unit can also be referred to as the pressing axis. The working axis can also generally be referred to as the advancing axis or feed axis of the respective tool. It is preferred at the present time that when using the device the fixed workpiece is deemed to be stationary, whereas the drilling unit or the press-in unit moves spatially in relation to the basic body and therefore in relation to the workpiece which is fixed thereupon. The disclosure, however, also embraces the kinematically reverse case that the processing unit together with the drilling unit and the press-in unit are stationary, whereas the workpiece is spatially movable. Since the working axes of the drilling unit or the press-in unit, if they are located in the working position in each case, at least in the main coincide, it can be ensured with higher precision that the press-in element is pressed into the hole with axial alignment. Lateral misalignment or angling is therefore excluded for the most part according to definition so that an eccentric or askew insertion or pressing of the press-in element into the hole is mainly avoided so that one-sided or spot damages to the material associated therewith and loosening of the press-in element associated therewith and finally a reduction of the extraction force can at least mainly also be avoided. The process reliability of introducing the press-in element into the workpiece can be further improved as a result. The terms mainly or at least in the main coinciding admittedly includes design-related and manufacturing-related tolerances, bearing clearances, etc., which can never be completely excluded. The working position can, but not necessarily, be lockable by latches, stops, or the like.
A particularly accurate positioning can be achieved when the processing unit is designed in order to guide the drilling unit and the press-unit in a combined movement. Meant by a combined movement within the meaning of the invention is that the drilling unit and the press-in unit move together, or are guided together, at least with regard to a spatial direction or rotational direction. Meant by a non-combined movement, in contrast to this, is that the drilling unit and the press-in unit can be moved, or can move, totally independently of each other. An example of a non-combined movement of movability would be an attachment on robot arms which can move independently of each other. In the case of a combined movement, tolerances can be added to a lesser extent than in the case of freer or independent movements of the drilling unit and of the press-in unit. Therefore, the accuracy of positioning of the drilling unit and of the press-unit can be improved as a result of a combined movement. The less the degrees of movement of the drilling unit and of the press-in unit are permitted, and the more the permitted degrees of movement of the drilling unit and of the press-in unit are intercoupled or fixed in relation to each other, the more this applies. The accuracy can in this sense mostly be improved when the drilling unit and the press-in unit are movable in relation to the fixed workpiece in only a single degree of freedom and they can only move together in this degree of freedom.
The device is advantageously designed so that the processing unit has a tool holder for accommodating the drilling unit and the press-in unit, wherein the tool holder is movably mounted in relation to the basic body and able to be driven, wherein the drilling unit and the press-in unit are fastened on the tool holder, and wherein the working position corresponds to a predetermined, preferably fixable, locked position or end position of the tool holder. In other words, in this embodiment the tools (the drilling unit and the press-in unit) move together with the tool holder which is mounted on the basic body. In this way, a combined movement of the drilling unit and of the press-in unit can be realized. The locked position or end position of the tool holder can be realized for example, but not exclusively, by stops or locking bolts or a toothed wheel engagement or the like. In an alternative embodiment, the tools can be movably guided or mounted individually on the processing unit. This can be effected and implemented via a displacement mimic, for example, which establishes at least one translational degree of freedom.
In a particular embodiment, the device is designed in such a way that the tool holder is mounted in a movable and drivable manner in relation to the basic body around a rotational axis. Rotational movements can be technologically easily controlled or implemented and have good kinematics. By means of the rotational movement of the tool holder, the drilling unit and the press-in unit can be swung into the working position and swung out of this in a simple manner. If the drilling unit and the press-in unit are fastened in a stationary manner on the tool holder (as seen relative to the tool holder), a combined movement of the drilling unit and of the press-in unit can therefore be realized in a particularly simple manner. In an alternative embodiment, the tool holder is mounted on the basic body in a linearly displaceable and drivable manner.
The rotational axis of the tool holder can, for example, be parallel to a processing surface of the workpiece. In this case, the drilling unit and the press-in unit are advantageously arranged so that the working axes are radial to the rotational axis of the tool holder (star-shaped arrangement). With this, at least one tool, i.e. either the drilling unit or the press-in unit, can be swung towards the workpiece so that the working axis is perpendicular to the processing surface. If the tool holder is rotated around the rotational axis, the one tool is swung away from the workpiece and another tool is swung towards the workpiece. As a result of this, for example when the drilling unit is swung towards the workpiece, which at the same time means that the press-in unit is swung away from the workpiece, the press-in unit can be easily accessible, as a result of which it can be easily equipped with a (following) press-in element.
In an embodiment alternative, the rotational axis can also be perpendicular to the processing surface, wherein the working axes are advantageously arranged parallel to the rotational axis (vertical turret principle). In contrast to the radial (star-shaped) arrangement of the working axes, the tools (drilling unit, press-in unit), in the case of a vertical turret-like arrangement, can be arranged altogether closer to the rotational axis and as a result of this the inertia moment of the processing unit together with the drilling unit and the press-in unit can be altogether lower. This can improve precision, setting speed and fatigue behavior of the device. As a further modification, an inclined arrangement of the rotational axis can be provided, wherein the rotational axes have an angle in relation to the rotational axis which corresponds to the inclined position angle of the rotational axis (conical turret arrangement).
In a preferred embodiment of the present invention according to this aspect, the drilling unit and the press-in unit, at least in part, are movable and drivable in the direction of their respective working axes in relation to the processing unit. For example, the press-in unit has a guide part and a press-in part, wherein the press-in part is mounted in the guide part in a linearly displaceable and drivable manner in the direction of the pressing axis (working axis) of the press-in unit. Equally, the drilling part can have a guide part and a drilling part, wherein the drilling part is mounted in a linearly displaceable and drivable manner and also rotatable and drivable manner in the rotational direction in the direction of the drilling axis (working axis) of the drilling unit. In other words, the advancing or feed movement for the drilling or pressing in is at least partially implemented by the drilling unit or press-in unit itself. In this case, lower masses are to be moved than when the entire tool holder is movable and drivable in the feed direction, which is possible, however. A movement or movability capability of the tool holder as a whole in relation to the workpiece, at least over a partial stretch of the feed path, can, however, be advantageous for a workpiece change, for example. If necessary, a feed movement or advancing movement towards the tool holder to or from the workpiece together with a fixing of the workpiece by way of the fixing unit can be carried out or coupled therewith.
In a preferred embodiment of the present invention according to this aspect, provision is made for a feed unit which is designed for the automatic feeding of press-in elements. This facilitates handling of the device since a manual equipping or collecting of the press-in elements from a support unit is not necessary. If, in addition, the feed unit is attached on the basic body, the feeding of the press-in elements, and possibly taking over by the press-in unit, can be enabled in a precise manner.
In a further preferred embodiment of the present invention according to this aspect, a plurality of press-in units for different types of press-in elements are provided on the processing unit. This facilitates the use of different press-in element. In this case, a separate feed unit can preferably be provided for each type of press-in elements. As a further option, a plurality of drilling units for different hole diameters can also be provided if the different types of press-in elements have press-in sections of different diameter.
In a development of the present invention according to this aspect, provision is made for a suction device which is designed for sucking up drilling residue. Dust, swarf, pieces, fiber portions, etc., for example, but not exclusively, can be understood by the term drilling residue. Particularly in the case of plastic or fiber composite materials, depending on the material used, or material of the matrix and/or fibers or material of a solid body, a possible static charge can make cleaning up of the drilling residues difficult. The suction device can preferably be fastened on the basic body and/or on the fixing unit or can be integrated altogether into the device. Alternatively, an external suction device can also be used.
In a development of the present invention according to this aspect, the fixing unit has a support element, which supports the workpiece from a rear side, and a clamping element, which clamps the workpiece from a processing side to the support element. By way of the support element and the clamping element, fixing of the workpiece can be implemented in an effective manner, wherein the support element additionally forms a counter support against a drilling or press-in force. The disclosure of this invention is, however, not limited to clamping in the previously described manner, rather a fixing of the workpiece can be implemented in a variety of ways. For example, provision can be made for grippers, which grip the workpiece from the side or in an opening (a penetration) of the workpiece, or a fixing of the workpiece can be effected by use of a negative pressure force, which, for example, is by suction cups or the like which are seated on the workpiece surface and subjected to a negative pressure.
In a development of the present invention according to this aspect, the press-in unit is designed in order to accommodate the press-in element with a clearance. By accommodating the press-in element with a clearance, the press-in element can additionally be aligned with the hole, wherein a bevel (chamfer), which is preferably provided on the press-in element, can be utilized.
In another or additional development of the present invention according to this aspect, the press-in unit is designed in order to elastically accommodate the press-in element such that the press-in element is retained on the press-in unit against external force action. As external forces, for example inertia forces, which are effective during movement of the press-in unit and shear force which is effective during normal operation, can be considered. In other words, holding by use of an elastic element, which holds the press-in element on or in the press-unit until the press-in element is pressed into the workpiece, is carried out. The elastic element can be an O-ring, for example. The retention force of the elastic element is in this case preferably designed so that the press-in element itself can be aligned with the edge of the hole when it is fed by the press-in unit in the direction of the workpiece. As a result, a misalignment in relation to the hole axis can largely be avoided. In order to avoid an angular misalignment, it can be provided that the press-in element is supported in a fixed manner (that is to say non-elastically, at least in the main) by the press-in unit in the feed direction.
In a further or additional development of the present invention according to this aspect, the press-in unit has a formed part, which is adapted to a formed section of the press-in unit, in order to accommodate the press-in element. As a result, formed features of the press-in element can be effectively utilized in order to accommodate it by the press-in unit.
In a preferred embodiment of the present invention, the press-in unit is designed in order to receive the press-in element from the feed unit while the drilling unit is in its working position. This can accelerate the processing cycle and is to be put into effect in a particularly simple manner in an embodiment of the device in which the press-in unit swings away from the processing point. Alternatively, feeding of the press-in elements can also be carried out directly at the processing point.
In a development of the present invention according to this aspect, the basic body is designed for the fastening of a processing machine or for manual handling. A processing machine can have, for example, but not exclusively, a robot arm or a portal guide or the like. If the basic body is designed for fastening on such an element of the processing machine, the device can be moved automatically by the processing machine and the processing operations can be automated in a particularly easy manner. Also, the processing point can be approached in a particularly accurate manner. The design for manual handling can, for example, but not exclusively, be implemented by hand grips, possibly supported by a bearing arrangement on a weight-balancing pivot arm, wherein release elements can be provided on the hand grips for the functional component parts of the device. In the case of manual handling, a variable application of the device in workshop or laboratory operation is also particularly simple.
In a preferred development of the present invention according to this aspect, provision is made for a computing unit. The computing unit is connected to the device or integrated into this and is constructed and designed to control the drilling unit so that when the hole is being introduced into the workpiece at least one parameter from the group which includes a feed speed, a rotational speed and an advancing force of the drilling unit is adapted to a predetermined drilling scheme. In other words, an open loop or closed control of speed, rotational speed or force can be carried out. The drilling scheme can especially preferably provide that a feed speed and/or an advancing speed is reduced at the commencement of the drilling and also shortly before penetration of a workpiece surface on the rear side. This can reduce a breaking away or delamination of the last laminate layers (especially in the case of workpieces consisting of carbon fiber-reinforced materials), which can occur in the case of excessively rapid drilling through. Optionally, the pressing-in process by use of the press-in unit can also be controlled by the computing unit with regard to advancing, press-in movement sequence (possibly also rotationally assisted) and/or pressing force. For feedback of the parameters, provision could be made for one or more suitable transducers which transmit(s) to the computing unit signals which represent forces, distances, moments or rotational speeds.
According to a further aspect of the present invention, a method is proposed for setting press-in elements into a workpiece, especially consisting of plastic or fiber composite material, such as CFK, wherein the method features the following method steps:
a) fixing the workpiece,
b) introducing a hole into the workpiece,
c) positioning a press-in element over the hole, and
d) pressing the press-in element into the hole,
wherein for carrying out the method use is made of a single device which intrinsically combines the functions which are required for realizing the method steps a) to d). The device can especially be the previously described device. The introducing of the hole into the workpiece can preferably be carried out while sucking up drilling residues in the region of the hole, and the positioning of the press-in elements over the hole can preferably be carried out with automatic feed of the press-in element. Finally, a step for quality assurance of the pressing-in process can be provided.
In a development of the method according to the invention according to this aspect, before carrying out the method steps a) to d), a pretreatment of the processing surface is carried out at least in the region of the predetermined point. A pretreatment can include any type of pretreatment which is suitable for optimization of the method. For example, roughing of the processing surface can especially improve the “cut” of a drill which is used when carrying out the method. Such roughing can, for example, but not exclusively, be carried out by sand blasting methods or blasting with another blasting material such as corundum. A further pretreatment possibility is the application of additional layers (films, lacquer, etc.) to the surface.
The method and the device according to the present invention can especially be adapted for the use of a press-in element consisting of metal, plastic, ceramic or fiber composite material particularly with carbon continuous fiber-reinforced composite material, for producing a load application point into a workpiece. The workpiece can preferably be a plastic workpiece or a fiber-reinforced, especially a long fiber-reinforced composite workpiece. A workpiece consisting of CFK can especially preferably accentuate the advantages of the present invention. The press-in element can preferably have a cylindrical section for pressing into the previously described hole. The cylindrical section can have a profile which is designed in order to increase the extraction load of the press-in element from the workpiece in relation to a smooth external contour. The press-in element can have a hole or an axially projecting bolt. The hole is preferably provided with a female thread or the bolt is provided with a male thread. As a result of this design of the press-in element, load application points or fastening points can be especially advantageously realized on the workpiece. Alternatively, the press-in element can also have a smooth surface which, for example, can be used as surfaces for the positioning of a weld point.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.